Preheat oven to 180C and line a baking sheet.
In a mixing bowl, cream together the butter, sugar, and eggs.
Once light and fluffy, mix in the vanilla essence and tahini.
In a separate bowl, add the sugar, flour, baking powder, and baking soda.
Mix together and add to the creamed tahini mixture.
Combine well and then stir in the chocolate chips
Roll cookie dough into small balls and place on the prepared baking sheet, leaving a 2-inch gap between each cookie as they will spread during baking.
Bake for 13 - 15 minutes, or until cookies are slightly golden brown around the edges.